We have measured the sky-projected spin-orbit alignments for three transiting Hot Jupiters, WASP-103b, WASP-87b, and WASP-66b, using spectroscopic measurements of the Rossiter-McLaughlin effect, with the CYCLOPS2 optical-fiber bundle system feeding the UCLES spectrograph on the Anglo-Australian Telescope. The resulting sky projected spin-orbit angles of $\lambda = 3^{ \circ}\pm33^{ \circ}$, $\lambda = -8^{ \circ}\pm11^{ \circ}$, and $\lambda = -4^{ \circ}\pm22^{ \circ}$ for WASP-103b, WASP-87b, and WASP-66b, respectively, suggest that these three planets are likely on nearly aligned orbits with respect to their host star's spin axis. WASP-103 is a particularly interesting system as its orbital distance is only 20% larger than its host star's Roche radius and the planet likely experiences strong tidal effects. WASP-87 and WASP-66 are hot ($T_{ eff}=6450\pm120$ K and $T_{ eff}=6600\pm150$ K, respectively) mid-F stars making them similar to the majority of stars hosting planets on high obliquity orbits. Moderate spin-orbit misalignments for WASP-103b and WASP-66b are consistent with our data, but polar and retrograde orbits are not favored for these systems.
Categories: astro-ph.EP